混合凋落物分解非加和性效应研究进展

混合凋落物的分解是陆地自然生态系统中凋落物分解的主要形式。在许多混合凋落物的实验研究中,混合凋落物的实际分解速率往往偏离于基于单种组分凋落物计算的预期分解速率,产生非加和性效应。从混合凋落物实验的统计结果可以发现,大多数混合凋落物实验的质量损失、养分释放、微生物丰富度和活性都表现出非加和效应。混合凋落物实验不同设计方案可能会对实验结果造成影响,如各组分的初始比例、凋落袋、取样和各组分的分拣均会对实验结果造成影响。引起混合凋落物分解非加和性效应的因素是多方面的,文章从物理、化学和生物作用机制三方面综述了非加和效应的潜在机制。未来的研究应模拟野外环境下凋落物的实际分解,并与气候变化、生态恢复等研究相结合。     

“非正常”凋落物对冰雪灾后南岭森林土壤有机碳的影响

2008年初,一场百年罕见的冰雪灾害袭击了我国南方地区,对南方19个省（区）的林区,相当中国森林面积的13%（1.86×107 hm2）的森林植被遭受整体性、毁灭性破坏,导致的大量“非正常”凋落物必将对森林土壤碳循环产生深远影响。本研究以广东乐昌杨东山十二度水省级自然保护区不同海拔梯度上受灾的常绿阔叶混交林3种森林群落为研究对象,采用去除冰雪灾害导致的“非正常”凋落物与受损林地进行对照试验,对冰雪灾害所导致“非正常”凋落物对土壤碳的影响进行了研究。研究结果表明：灾后3种森林群落中不同深度土壤的有机碳质量分数和储量持续增加,同一深度土壤有机碳质量分数和碳储量在不同年份之间差异显著。直至2011年“非正常”凋落物分解完毕时,10~50 cm的土壤有机碳质量分数与上一年相比有减少趋势;0~10 cm的土壤有机碳质量分数稍比2010年高,但变化差异不显著(p=0.36),说明在“非正常”凋落物分解结束后土壤有机碳质量分数有减小的趋势,致使土壤碳储量下降。去除“非正常”凋落物样地与对照样地相比,各土壤深度的土壤有机碳质量分数明显下降,年平均下降百分比例变化范围为12.14%~55.34%,0~10 cm和10~30 cm土壤的有机碳质量分数下降变化波动幅度要比30~50 cm大;不同深度土壤有机碳质量分数与凋落物有机碳失质量间具有显著的线性相关性。可见,冰雪灾害导致的“非正常”凋落物对土壤有机碳质量分数和储量都有十分显著的影响,“非正常”凋落物的分解输入能显著提高土壤有机碳质量分数和储量。     

森林枯枝落叶分解及其影响因素

枯枝落叶在森林生态系统中占有极其重要的地位,枯枝落叶的分解是一个以生物为主要参与者的过程,土壤动物使粗枯落叶实现物理性分解,土壤微生物则使枯落物碎片进一步分解为简单无机分子或转化为腐殖物质。土壤微生物的分解受枯落物自身成份的影响,粗脂肪与可溶性糖等在前期分解,木质素与纤维素等在后期分解,低w(C)/w(N)比枯落物易于分解,枯落物内的有机氮最终将降解为NH 4和NO-3,用于描述枯落物分解的最常用模型是指数方程x/x0=e-kt。自然因素与人为因素引起的火烧也是引起地面枯落物消失的重要因素,它有很强的负面效应,造成有机氮的损失。影响枯落物分解的因素很多,它们主要是通过影响分解生物而起作用,这些因素有树种、温度、湿度、酸碱度、污染等。阔叶树枯落物通常比针叶的分解快,温度与有机氮的矿化有线性关系,硝化作用可在大幅度的温度范围内发生,但最适温度通常在25℃。碳矿化的最适含水量约60%,在过于淹水条件下易于出现反硝化作用而造成氮损失。森林枯落物分解以真菌为主,适于在较高pH条件下进行,但与枯落物种类有关,云杉最适分解酸度为pH5～7,多种阔叶树最适分解酸度在pH3.5,土壤变酸时通常造成细菌数量显著下降,而以真菌占主导。枯落物的处理方式影响森林土地的生产力,移除地面枯落物或采伐剩余的枝叶可造成土地肥力的显著下降,相反,则有利于维持土地肥力。     

三江平原典型环型湿地主要植物群落枯落物的热值变化

研究了小叶章(Calamag rostis angustifolia)、毛果苔草(Carex lasiocarpa)和漂筏苔草(Carex pseudocuraica)群落枯落物在1个生长季内的分解热值变化特征,并初步探讨其影响因素。环型湿地3种植物群落由于各自的微环境不同致使其枯落物热值变化有所差异。6月至10月,小叶章群落枯落物热值呈现逐渐下降趋势,而毛果苔草群落和漂筏苔草群落由于所处环型湿地位置不同而形成不同于小叶章群落的湿地水热条件,从而造成其枯落物热值的总体变化趋势是先下降再上升,最后又下降。同时,同一群落不同深度枯落物热值变化也不同。0—10、10—20和20—30 cm土层热值变化相似,而30—40 cm土层热值变化规律不明显。     

Global Analysis of Anthropogenic Debris Ingestion by Sea Turtles

Ingestion of marine debris can have lethal and sublethal effects on sea turtles and other wildlife. Although researchers have reported on ingestion of anthropogenic debris by marine turtles and implied incidences of debris ingestion have increased over time, there has not been a global synthesis of the phenomenon since 1985. Thus, we analyzed 37 studies published from 1985 to 2012 that report on data collected from before 1900 through 2011. Specifically, we investigated whether ingestion prevalence has changed over time, what types of debris are most commonly ingested, the geographic distribution of debris ingestion by marine turtles relative to global debris distribution, and which species and life‐history stages are most likely to ingest debris. The probability of green (Chelonia mydas) and leatherback turtles (Dermochelys coriacea) ingesting debris increased significantly over time, and plastic was the most commonly ingested debris. Turtles in nearly all regions studied ingest debris, but the probability of ingestion was not related to modeled debris densities. Furthermore, smaller, oceanic‐stage turtles were more likely to ingest debris than coastal foragers, whereas carnivorous species were less likely to ingest debris than herbivores or gelatinovores. Our results indicate oceanic leatherback turtles and green turtles are at the greatest risk of both lethal and sublethal effects from ingested marine debris. To reduce this risk, anthropogenic debris must be managed at a global level. Análisis Global de la Ingesta de Residuos Antropogénicos por Tortugas Marinas     

Fire in the woods or fire in the boiler: Implementing rural district heating to reduce wildfire risks in the forest–urban interface

Many rural communities in British Columbia (western Canada) are at risk from wildfire. This risk will increase over time as a result of climate change because of higher average temperatures, longer growing seasons, and more intense droughts. On the other hand, these communities are also faced with rising fuel costs and a growing demand for heat as suburban population increases. The fact these communities are surrounded by forests presents an opportunity to combine community wildfire risk abatement with bioenergy development. Additional co-benefits include: (1) reduced community energy expenditures; (2) the creation of local jobs; (3) climate change mitigation; and (4) increased community energy security. Here, we present results from three pilot rural communities (Burns Lake, Invermere, and Sicamous, all of them in British Columbia) designed to evaluate the feasibility of wildfire risk abatement in conjunction with bioenergy production. Maps were created showing each community's forest–urban interface area with quantified estimates of its sustainable woody biomass resource potential under different management scenarios while monitoring ecosystem and soil health. The results and experience gained through this work has been synthesized in a calculator tool to help other communities make their own screening-level assessments. This calculator is a freely available on-line tool: FIRST Heat.     

珠江三角洲四种森林类型土壤CO2通量特征研究

采用开路式土壤CO2通量测量系统Li-8100&Li-8150对珠江三角洲地区尾叶桉(Eucalyptus urophylla)人工林、乡土树种恢复林、针阔叶混交林和常绿阔叶林4种林型的土壤CO2通量进行了观测。结果表明:4种森林类型年均土壤CO2通量为尾叶桉人工林(3.35μmol.m-2.s-1)>针阔叶混交林(2.66μmol.m-2.s-1)>乡土树种恢复林(2.09μmol.m-2.s-1)>常绿阔叶林(1.86μmol.m-2.s-1);旱季土壤CO2通量明显小于雨季。前3种森林类型凋落物呼吸处理表明,旱季对照组土壤CO2通量均小于相应的去除凋落物组、雨季则相反,全年的对比结果显示,3种森林类型的凋落物呼吸贡献分别达到1.3%、7.1%和10.8%。土壤CO2通量与10 cm土壤温度呈显著指数相关,且土壤CO2通量温度敏感指数表现为针阔叶混交林Q10最大(3.49),尾叶桉人工林Q10最小(1.95)。     

UV-B辐射对亚热带森林凋落叶氮、磷元素释放的影响

UV-B辐射对凋落物分解过程的影响已成为全球变化生态学研究中的前沿和热点问题之一.采用分解袋法对自然和UV-B辐射滤减两种环境下亚热带6种代表性树种(杉木、马尾松、木荷、香樟、青冈和甜槠)凋落叶氮、磷元素的释放动态进行了研究.结果表明,凋落叶氮元素的动态表现为直接富集、释放-富集和释放-富集-释放3种模式,磷元素的动态表现为直接释放、富集-释放-富集和无明显变化3种模式.与对照相比,UV-B辐射滤减显著延缓了甜槠凋落叶氮元素及青冈和甜槠凋落叶磷元素的释放(P<0.05),但促进了香樟凋落叶磷元素的释放(P<0.05),对其他树种凋落叶的氮或磷释放无显著影响.凋落叶的初始氮含量和C/N比值不能解释氮释放动态,C/P比值可以部分解释磷的释放.全球环境变化背景下UV-B辐射在湿润亚热带地区森林生态系统过程中的作用尚需进一步认识和理解.     

长江上游高山森林林窗对凋落物分解过程中可溶性碳的影响

采用凋落物分解袋法, 以川西高山森林典型乔木(四川红杉Larix mastersiana、岷江冷杉Abies faxoniana、红桦Betula albo-sinensis和方枝柏Sabina saltuaria)和灌木(高山杜鹃Rhododendron lapponicum和康定柳Salix paraplesia)凋落物为研究对象, 研究了林窗中心到郁闭林下不同生境(林窗中心、林冠林窗、扩展林窗和郁闭林下)中凋落物第一年分解不同关键时期(雪被形成期、雪被覆盖期、雪被融化期和生长季节)可溶性碳的动态特征。结果表明:6种凋落物可溶性碳和可溶性有机碳在冬季含量增加而在生长季节含量降低, 而可溶性无机碳含量在全年呈降低趋势;雪被形成期, 6种凋落物可溶性碳和可溶性有机碳在郁闭林下达到最大值, 而雪被覆盖期在林窗中心和林冠林窗达到最大值, 生长季节6种凋落物可溶性碳含量均低于初始含量。这表明全球气候变暖情景下, 冬季林内雪被覆盖时间和厚度降低且生长季节延长将减少凋落物可溶性碳含量, 且变化程度受到凋落物质量控制。     

Composition of Aqueous Extracts of Broiler Litter Treated with Aluminum Sulfate,Ferrous Sulfate,Ferric Chloride and Gypsum

More knowledge on the composition of aqueous extracts of broiler litter amended for Water Soluble P (WSP) reduction would help to understand how amendments work. We measured pH, concentrations of Ca, Mg, Fe, Al, Cu, Mn, Zn, Molybdate Reactive P (MRP), and Dissolved Unreactive P (DUP) in water extracts of broiler litter treated with aluminum sulfate (ALS), ferrous sulfate (FES), ferric chloride (FEC), and gypsum (GYP) at 0, 5, 15, and 25% w/w. In order to study the effects of acidification, the same properties were measured in aqueous extracts of broiler litter suspensions that were titrated to end-points 3, 4, or 6 with 0.5N HCl. Concentrations of MRP, DUP, Ca and Mg, were 61%, 53%, 3.8 times, and 2.6 times greater in extracts from suspensions acidified to pH 6 than at the original pH of 8.9. ALS, FES, and FEC reduced pH, and showed similar effects on WSP concentrations, which were greater than with GYP. The magnitude of the reductions in WSP by ALS, FES, and FEC is uncertain because the actual amount of WSP immobilized cannot be determined. This is because of two opposite effects: 1) Through adsorption, soluble aluminum and iron remove phosphates from solution, and 2) Through acidification, iron and aluminum compounds release phosphates to solution.